very interesting writeup and analysis. good luck!

 

According to that link, the average piece of paper is 1/1000 in. thick. I thought paper was like 4-6 thousandths of an inch thick, but I haven't checked in a long time.

 

1/1000's was the unit of measure for the legend in the table. Here are all of the actual measurements:

TEXT PAPERS 25x38
50# OFFSET .0040 60# ENAMEL .0030
60# OFFSET .0045 70# ENAMEL .0045
70# OFFSET .0050 80# ENAMEL .0040
100# OFFSET .0070 100# ENAMEL .0050

 

.004 in = 4 thousandths of an inch, not 40 thousandths.

I was wondering about the "1/1000 in" thing. They have that, but still give the values as ".004 in" and not "4".

 

Yes, .004 is 4 thousandths, but that's not what the table says is it? Read the numbers outlined in bold again.

A little math refresher course:



But hell, I like to play devil's advocate as much as the next guy, so let's just go along with your standard of measurement and use it as a point of reference. So let's just say that a sheet of paper is 4 thousandths of an inch thick: this would mean that the area of tolerance that the tech at MSD had determined was too far out of spec was actually ten times smaller than that. So now, the "o-ring pinch" which led to the backing plate being bent had bent it so severely out of spec that we couldn't even fit 1/10th the width of a sheet of paper into the used up clearance.

Sound ridiculous enough yet?

 

First underlined sentence says:
This caused the black backing plate under the rotor to bow up and rub the back of the rotor. He said my plate was bowed about 30 thousands in the center.

Second underlined sentence says:
I am not sure how the billet back plate could flex enough to cause the bowing he described.

One contradicts the other as the 'black backing place' is not the 'billet back plate? It makes some sense to me that the black [intermediary?] plate could bow or be 'raised' .030 [thirty thousandths] by a folded oring.. and that would cause the rotor to rub as described..
Hard to believe that it wouldn't be noticeable tho, at least upon your inspection after removal? Did you take the rotor and plastic black plate off before sending it back to MSD?


soundandthefury:

The paper thickness table:
TEXT PAPERS 25x38
50# OFFSET .0040 60# ENAMEL .0030
60# OFFSET .0045 70# ENAMEL .0045
70# OFFSET .0050 80# ENAMEL .0040
100# OFFSET .0070 100# ENAMEL .0050

is in ten thousandths... [.0040=40 tenthousandths]

Not sure what you mean here:
So let's just say that a sheet of paper is 4 thousandths of an inch thick: this would mean that the area of tolerance that the tech at MSD had determined was too far out of spec was actually ten times smaller than that. So now, the "o-ring pinch" which led to the backing plate being bent had bent it so severely out of spec that we couldn't even fit 1/10th the width of a sheet of paper into the used up clearance.

The tech said .030 thirty thousandths.. which [assuming paper thickness of .004" ] is 7.5 paper thicknesses.. not one tenth?
That's about 1/32" which I suppose COULD raise the black plastic piece enough to rub on the rotor like that.. [not saying that's what happened but it is plausible]

 

I have a question. I read the instructions from MSD, isn't the MSD drive pin indexed too? So, why do we have too remove the cover to ensure the rotor is lined up with the old unit. We don't have to do this with the factory replacement.

 

I haven't seen an MSD in person, but would think it was indexed like the stock opti?..
I think they want it done that way to make it idiot proof, tho I can't think why they would want you to take the cap off unneccessarily tho.. that can cause more problems than it cures..
I would be inclined to remove it for a look see and check tightness of screws etc anyway tho..
Actually surprised the unit isn't factory sealed..

 

Why am I suddenly starting to feel like I'm trapped in The Twilight Zone's version of "The Mr. Obvious Show?"

 

I guess my Q then is do you know the difference between thousandths and ten thousandths of an inch?
.001= 1 thousandth
.0001 =1 tenthousandth...
I just can't understand why you think .030" [30 thousandths] is '10 times smaller than the thickness of one piece of paper' [.0040] when it's the [approx] thickness of 7.5 sheets of paper?
What am I missing here?
Not trying to be critical here.. but I just don't get what you're saying?

.030" is about 1/32" a rather substantial amount..

 

I can't believe you guys are confused over measurements of .004" vs .040"...

.004" = 4 thousandths
.040" = 40 thousandths

some examples
a head gasket is typically .039"-.050" thick
binder paper is .003" (measured just now)
dvd is about .050-.060"

 

And .0040 is 40 tenthousandths
'You guys' aren't confused, but I think someone is..
I am politely trying to correct it...
Apparently w/o much success...
Someone else try, I give up...

 

I am preparing to install and MSD opti unit also and will be extremely careful after rading this post!

ps..

guys in laymens terms..

how much is 1,000? one thousand..

how much is 10,000? ten thousand

so...

.040 = 40 x .001 = forty one thousands of an inch

.0040= 40 x .0001 = four one thousands of an inch

as such.. at .009, the next number is? thats right .010 when increasing the tenths push to the left towards the decimal.. hence it goes from nine thousands, ten thousands, eleven thousands... until you hit the whole number 1.

don't believe me.. try gapping your plugs to "forty thousands" with a piece of paper and get back to me on how she runs!


Chris

 

Thank you. I knew that a piece of paper wasn't 40 thousandths thick. I kind of accidently knocked this thread off topic. I apologize for that.

 

Well got most of my underhood appart, still have the pass. side manifold to remove, but otherwise I should be ready to start installing my new opti/headers as soon as I get back from holidays next monday. Hopefully the MSD holds up 'cause this would suck doing more then once, lol (although I've done it a few times on my old car).